Process of polymerizing acrylamide



Patented Oct. 25, 949 2,486,191

UNITED STATES PATENT OFFICE PROCESS OF POLYMERIZING ACRYLAMIDE Louis M.Minsk, William 0. Kenyon, and John H. Van Campen, Rochester, N. Y.,assignors to Eastman Kodak Company, Rochester, N. Y., a

corporation of New Jersey No Drawing. Application July 22, 196, SerialNo. 685,378

4 Claims. (01. 260-89.?)

1 2 This invention relates to a process of conalone. More specifically,the alcohol employedin trolled polymerization and more particularly toour process can be, for example, methyl, ethyl, a process for obtainingwater-soluble polyacrylpropyl, isopropyl or tertiary butyl alcohols, andamides and alpha-methacrylamides of variable the catalyst can be awater-soluble type, i. e., molecular weights from monomeric acrylamide 5one which is soluble in the solvent mixture, such and methacrylamide. ashydrogen peroxide, potassium persulfate, so- It is well known that themethod employed in dium perborate, and other similar kind of comthepolymerization of an unsaturated compound pound. markedly influences thephysical and chemical structurally, the polymers obtained by ourcharacteristics of the resulting polymeric prodlo process of controlledpolymerization can be repuct. For example, polymerizations conducted inresented by one of the following structures, demass generally favor theformation of insoluble pending on whether the polymerization of thethree-dimensional type polymers, [Moureau-Ann. monomeric acrylamide t ks place in a random chim. (7), 2, 175 (1894); Staudinger and Urechorder,head to tail, or head to head, tail to tail, Helv. chim. Acta 12, 1107(1929)], whereas polysequence: merizations brought about in solution ofan inert solvent, due to the proximity of the chains being greatlyreduced, generally favor the formation of 0:0 0: =0 linear polymerspossessing greater solubility and 1 in some cases lower molecularweights. Various H esters of acrylic acid and alpha-methacrylic acid 4have been polymerized in alcohol solutions con- (Head to tan) tainingsubstantial proportions of water, the

products being of lower molecular weight and inr (fHCH CH,-(EH-CH-CHsoluble in the alcohol-water polymerization medl- 2o =0 =0 0:0 (i= ums.Still other polymerizations of various esters 1 1 NH of acrylic andmethacrylic acids have been made H in alcohol-water mixtures, in whichthe polymers (Head to head, M to mm were insoluble, in order to obtainthe polymeric p du s in th f m f mushy r i m ss The above formulas areonly illustrative with no which were more readily workable into finelydlattempt made to place the respective groups upon vided states for themanufacture of molding comquantitative ti i However, for mpositions,lacquers and the like. Other products gi purposes, th t r ombinedacrylic a id" have been prepared by polymerizations in water refers t thgrgup in the presence of per-salts such as ammonium persulfate, benzoylperoxide and hydrogen perox- CH ?H COOH ide. However, none of thesemethods describe a I means for obtaining polyacrylamides of desired theterm acrylamide" to the group molecular weight and solubility. cH, cHc0N We have now found that by polymerizing monl omeric acrylamide ormonomeric methacrylamide u in awater medium containing fromapproximateand the term acrynmide to the group 1y 5 to 40 per cent byvolume of a water-miscible Fem-(I334? WINE alcohol, in the presence of acatalyst, for example, hydrogen peroxide, water-soluble polyacrylamidesIt is, accordingly, an object of our invention of controlled molecularweight can be obtained, to provide a process for preparing water-solubledepending upon the, volume per cent of alcohol polyacrylamides of thekind above described. Anin the polymerization mixture of water andalother objectis to provide a process for preparing cohol. Assuming thatconditions of temperature such water-soluble polyacrylamides in a conandconcentrations of catalyst and monomer are trolled range of molecularweight. Other objects constant, with increasing amounts of alcohol, willbecome apparent hereinafter. there are obtained polymers ofprogressively de- It is an established fact that the viscosity ofcreasing molecular weights. .The most viscous a polymer in solution issubstantially a direct and correspondingly higher molecular weightmeasure of the molecular weight of the polymer, polymers are obtained bypolymerization lnwater i. e., for a given solids content, the lower themolecular weight of the polymer the lower will be the viscosity of thesolution containing it. For the purpose of our invention, the molecularweights are presented in terms of specific, intrinsic and relativeviscosities. The specific viscosity can be determined in water at aconcentration of 0.100 gram of the polymer per 100 c. c. of solution,the now times being determined in an Ostwald viscosimeter at atemperature of 25 0., and is calculated from the measured flow time ofthe solution, divided by the flow time of the solvent alone, minus one.The intrinsic viscosity can be used in place of specific viscosity andis defined by the following equation:

in which or is the relative viscosity of a dilute water solution of thepolymer divided by the viscosity of the water in the same units and atthe same temperature, and C is the concentration in viscosities of thepolyacrylamides obtained by polymerizing acrylamide in the variouswater-a1- cohol mixtures as compared to the polyacrylamide obtained whenpolymerization is made in water alone, the viscosity of the polymerobtained in water alone has been taken as unity and the viscosities ofthe polymers obtained in water-alcohol mixtures, in the same. series,have been calculated to fractional values termed viscosity ratio." Forexample, the viscosity ratio of a polyacrylamide obtained bypolymerizing acrylamide in a 70-30 water-methyl alcohol mixture is givenin Table II as 0.528, and was calculated by dividing its intrinsicviscosity value of 0.93 by the intrinsic viscosity value of 1.76 for thepolymer obtained by polymerizing acrylamide in water alone.

The process of this invention is described more specifically in thefollowing examples:

EXAL/IPLE 1.-POLYMERIZATION OF ACRYL- AMIDE IN WATER-ETHANOL MIXTURESThe acrylamide was prepared by passing dry ammonia gas into acrylylchloride dissolved in dry benzene. After filtering off the ammoniumchloride, the filtrate was chilled and the acrylamide obtained in theform of crystals. The crystals were purified by recrystallization frombenzene and dried under constant vacuum. The melting point of thepurified crystals of acrylamide was 85.0-85.2 C., and the nitrogencontent 19.53 per cent by weight as compared to calculated theoreticalof 19.72 per cent.

In all-glass reflux units, there were placed 200 c. 0. volume ofwater-alcohol mixtures of the compositions given in Table I. To each. ofthese mixtures were added 20 grams of acrylamide, prepared as abovedescribed, and 0.8 c. c. of 30 per cent hydrogen peroxide. The reactionswere heated in a 90 C. bath for a period of two and one-half hoursThejviscosities of the dopes so obtained were'found to be in decreasingorder with increasing amount of ethanol." The sample containing-40 percent-of alcohol turned cloudy on cooling, whereas the 50 per centsamplewas cloudy at 90 C. I The samples were precipitated by pouringinto excess of ethanol, the precipitates extracted ,with fresh' portionsof ethanol and dried first in a'vacuum' desiccator underconstant vac-Condition of hot Intrinsic Ratio Solvent I viscosity dofieaiiggigglyg lfw 0 star Weter'only I Methylaloohol .e. Ethyl alcohol 0.315

' n-propylaleohol. 0.250 lsopropyl alcohol 0.136 Tertiary butylalcohoi0.824 v uum, and then to constant weight at 55". C. at

atmospheric pressure. The specific viscosities of the respective sampleswere then determined in an Ostwald viscosimeter at 25 C., at aconcentration of 0.100 gram made up to 100 c. c. in distilled water.

TABLE I Eflect of alcohol concentration on the viscosity of obtainedpolyacrylamide Per Cent Specific Viscosity Ratio Alcohol by ViscosityWater-Alco- Volume in Water hol/Water In place of acrylamide in theabove example, there can be substituted alpha-methacrylamide to obtain asimilar series of related products decreasing in molecular weight withincreasing amount of alcohol in the polymerization mixtures.

EXAMPLE 2.-POLYMERIZATION OF ACRYL- AMIDE IN -30 WATER ALCOHOL MIX-TURES In all-glass reflux units, were placed acrylamide, prepared in themanner described in Example 1, and mixtures of water and alcohol in theratio of one gram of acrylamide to 10 c. c. of the water-alcoholmixture. The mixtures of water and alcohol had been previously made upby volume, and the amount required in the diiierent polymerizations wereremoved from the stock solutions. To the polymerization mixture in eachsample was added 30 per cent hydrogen peroxide in an amount equal to0.04 c. e. per gram of acrylamide. The polymerization mixtures were thenheated in a C. bath for two and one-half hours. Simultaneously, acontrol using water only as the polymerization solvent was run. In those,cases where precipitation had occurred, water was added to the reactionmixture after polymerization to effect re-solution of the precipitatedpolymer. The dopes were then precipitated in absolute ethyl alcohol andthe precipitated polymers thoroughly extracted with fresh portions ofabsolute ethyl alcohol. The polymers were dried in a vacuum desiccatorunder constant vacuum. The intrinsic viscosities were determined in eachcase at a concentration of 0.250 gram of polymer in c. c. of watersolution. The results are shown in Table II and III for mixtures of70-30 water-alcohol and 6040 water-alcohol for methyl, propyl, isopropyland tertiary butyl alcohols.

TABLE II Polymerization of acrylamidein 70:30 water-alcohol mixturesr'miu Table I.

TABLEIII Polymerization of acrylamide in 60:40

' water-alcohol mixtures Viscosity Condition of hot Intrinsic RatioSolvent dope alter poly- Visoosit Water-Alcoy merlzation hollwatcrWateron1y 2.40 Clear 1.000 Methyl alcohol 1. l7 do 0. 488 Ethyl alcoholdo l 0. 252 n-propyl alcohol 0. 44 Turbid. some pre- 0.183

cip tatlon. Isopropyi alcohol. 0, 29 Turbldm 0. 121 Tertiarybutylaicohol 1.77 Turbid, with pm- 0.737

cipitation.

I From Table I.

The polyacrylamides vprepared by our controlled process ofpolymerization in water-alcohol mixtures are water-soluble and arecharacterized by having a content of about per cent by weight ofacrylimide groups, less than one per ratio of 1 gram of acrylamide to 10c. c. of the mixture consisting of from 60 to 95 parts by volume ofwater and from to 5 parts by volume or ethanol, and heatingthe resultingsolution at a temperature of 90 C. in the presence of 0.04 c. c. of 30per cent hydrogen peroxide to each gram of acrylamide hydrogen peroxide.

3. A process for preparing a water-soluble polyacrylamide whichcomprises dissolving acrylamlde in a mixture of water and alcohol in theratio of 1 gram of acrylamide to 10 c. c. of the mixture consisting offrom'60 to 95 parts by volcent of combined acrylic acid groups, but insome' cases as high as 3 per cent where polymerization heating periodhas been unduly prolonged, and

the balance polyacrylamide groups, and further characterized by the factthat their aqueous solutions are unaflected in solubility, when the pHand temperature of the solutions are lowered.

What we claim is:

1. A process for preparing a water-soluble polyacrylamide whichcomprises dissolving acrylamide in the ratio of 1 gram of the acrylamideto each 10 c. c. of a mixed solvent consisting of from to 95 parts byvolume of water and from 40 to 5 parts by volume "oia completelywatermiscible, saturated mo 7 ohydroxy aliphatic alcohol containing from1 to 4 carbon atoms, and heating the resulting solution at a temperatureof C. in the presence of 0.04 c. c. of 30 per cent hydrogen peroxide toeach gram of acrylamide.

2. A process for preparing a water-soluble polyacrylamide whichcomprises dissolving acrylamide in a mixture of water and alcohol in theat a temperature of of isopropanol, and heating the resulting solutionat a temperature of 90 C. in the presence of 0.04 c. c. of 30 per centhydrogen peroxide to each gram of acrylamide hydrogen peroxide.

LOUIS M. MINSK. WILLIAM O. KENYON. JOHN H. VAN CAL IPEN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,289,540 Dittmar et al. July 14,1942 FOREIGN PATENTS Number Country Date 487,402 Great Britain June 11,1937 475,671 Great Britain Nov. 24, 193'!

